The sequence upstream of the first codon in the mRNA is the Shine-Delgarno sequence. It is site that the 30S ribosome interacts with that recruits the binding of the 50S subunit in *E.coli*. This forms an intact ribosome and the initiation complex.

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The initiation complex begins translation of proteins. In *E.coli*, the 30S ribosome interacts with the mRNA template, along with initiation factors. 
Guanosine triphosphate is needed as energy for this process. Initiation of translation requires formylated methionines to begin.  

Key terms for translation initiation in prokaryotes: 
1. tRNA N-formyl-methionine (fMet-tRNA^fMet)
2. Shine-Delgarno sequence

Initiation of Translation in Prokaryotes

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The initiator tRNA carries a N-formyl-methionine (fMet) that interacts with the AUG codon of the mRNA. This fMet is the first amino acid in the proteins in *E.coli*.

tRNA with N-formyl-methionine 

Shine-Delgarno Sequence

The *E. coli* ribosome has been well studied and is the model for prokaryotic transcription. The *E. coli* ribosome has two subunits: the 30S and the 50S. In translation initiation, the 30S recognizes the Shine-Delgarno sequence and then the 50S subunit can interact with the 30S to form the assembled ribosome for translation.

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